Choosing and Using Dehumidifiers
To Dry Out Your Home

Dehumidifiers are just one more way that man has taken control of his environment.

Without them, the usefulness of basements and even some homes in very damp areas would be very limited... mostly to growing mushrooms and designer mildew. Thank you, Mr. Dehumidifier, wherever you are!

What is a dehumidifier and how does it work?

A dehumidifier is essentially a refrigerator that forgot to get fully dressed. Really. The basic mechanical function of a dehumidifier is the same as a refrigerator. Compression and expansion of a gas is used to lower the temperature of metal coils to freezing temperatures.

However, instead of the cooling action being directed into a closed box, a dehumidifier is designed to blow warm moist room air over these cold coils. The moisture in the room air condenses on the coils to become liquid water. The water then drips into a drip collection pan, or to a drain. The room air, now freed of much of its moisture, returns to the room slightly warmer than it was. Dehumidifiers are controlled by a device known as a humidistat. This is an adjustable rotary switch which detects moisture in the room's air. It automatically turns the dehumidifier on or off as it is needed, based on the setting you choose. If you wish, you can set the dehumidifier to the maximum setting for continuous operation.

Why would I want to purchase one?

If you store anything of value in your basement, or if you use your basement as living space, it is important to keep the moisture level low. Unlike the rest of your home, the parts of your foundation that are below ground level, or "grade", is constantly in contact with moisture from the earth outside. Though some homes have adequate vapor and water barriers installed outside their foundations, many older homes have none.

This moisture can cause mildew growth and damage to furniture of all types, photos, carpets, and virtually anything except the dog. It is a sad fact that every year people unknowingly destroy their valuable possessions by not taking steps to lower the level of moisture in their basement's air.

How big a dehumidifier should I buy?

Good question, but the answer is unclear. There are arguments for both large and small dehumidifiers. Large ones remove moisture faster, so they operate for shorter periods of time. However, there is more electricity used per hour to run a larger dehumidifier.   Since more electricity is used at "start-up" than during any other time in the cycle, some of the apparent cost benefits of large size are lost. Considering that larger units are also more expensive to purchase, there may be little or no benefit to buying an oversized unit for most people.

Bigger can at times really be better!  The advantages of size are most noticeable when dehumidifying a large area.  A small dehumidifier may run continuously and still never lower the humidity to an acceptable level.  A larger unit, by dehumidifying a larger amount of air per hour, can keep up with the demands of a large room.

Do I need someone to install it?

That depends. Since the condensed water drips from the coils it has to go somewhere. If your basement has only a small moisture problem and you don't mind carrying the drip pan outside or to a sink, just put the dehumidifier on the floor and plug it in. It will shut off automatically when the drip pan is full... hopefully. This is not the most fun way to live with a dehumidifier... the drip pans (especially on the larger units) hold a lot of water and can be quite heavy when full. Actually I'm still waiting for a model that will call me so I don't have to keep checking. (By name!)

The solution nonpareil is to install your dehumidifier so that it is self-draining. If you have a sink or toilet in the basement, or even a lowly floor drain, place the dehumidifier on a table or a shelf and run a hose from the drip pan to the drain.

If you do not have a drain you can still make your unit self-draining, but things get more complicated. Since dehumidifiers do not pump water upwards, you may need to install a sink pump. This is a special enclosed pump designed for non-sewage use to move waste water upwards to your plumbing drain pipes. It will work with sinks, washing machines, water softeners, and... yes, dehumidifiers. Here you go, guys! Always wanted that sink in the basement, right?  Now you have a great excuse... uhh...  logical reason!

Another alternative is to put the dehumidifier on a table or shelf so that it can drip into a large container, such as a 5 gallon bucket on the floor. This will decrease your number of trips for sure, and will probably give you forearms like Popeye from carrying that heavy bucket upstairs. The only drawback... this is a biggie... is that the dehumidifier will have no way to know if the bucket is full, so it will continue to run even after the bucket is full and overflowing all over the new carpet! So, when you go on vacation, disconnect the hose from the drip pan and screw a garden hose cap on the hose pan's nipple (ouch!). Then, you can at least run the dehumidifier until the pan fills.

Should I use a dehumidifier year round?

That depends on the temperature of your basement and your local climate.   Dehumidifiers do not function well at lower temperatures, so under 65 degrees it is almost a waste of money to run them. Plus, as the air temperature drops, the risk of freezing the coils increases (read the next question for more on freeze-ups). If you heat your basement, the warm air will move moisture from the basement to the house above, keeping the humidity lower in the basement and slightly humidifying the rest of the house.

In areas where the ground is frozen for most or all of the winter, the amount of moisture that will migrate through the basement floor and walls will drop dramatically in the winter, so the need for dehumidification decreases. However, if you live in a temperate area, and your basement is not heated, you may have to run the dehumidifier year round.

Is there any maintenance to perform?

You should check the coils at least seasonally and keep them clear of dust and dirt. If the unit has a removable front cover, there may be a foam filter inside that should also be cleaned.

The purpose of this cleaning is two-fold. First, dust and dirt can insulate the coils from the room air, decreasing the efficiency of the dehumidifier. Secondly, this same dirt will get damp and possibly freeze. Freezing is the most damaging thing that can happen to your dehumidifier because it will run continuously but not dehumidify the air. This will lessen the life of the unit and lighten your purse when the unit suffers a premature death! Not to mention the bill your smiling utility man will hand deliver with a "Thank You" note from the electric company.

What brand should I buy?

I don't do product testing. Not that I wouldn't enjoy doing it, but I have toasters to clean and socks to sort.

When I purchase a new product, especially an expensive appliance, I always ask myself, "If this product needs service, or parts, can I get them locally?" I also ask myself, "Will this company be in business in a year... or 5 years?" So I tend to make these types of purchases from established local dealers, or choose a brand name that I have had experience with, either with other of their products or based on their reputation. Then...  I go bargain hunting!

You can, of course, try to find back issues of product evaluations in magazines but I have found that to be a fruitless exercise most of the time. My experience has been that the reports they give are often for products and models that you can't find in local stores. It's telling and a sign of the times that so many companies don't keep their products on the shelves long enough for us to figure out if they are any good! Go figure.